Manufacturing processes for automobiles have evolved from one that utilized MIG welding processes, i.e. a welding process in which a line of molten material is deposited by the welder in joining two pieces of metal together. Spot-welding, a process involving the passage of electrical current between two electrodes to melt and join two pieces of metal placed between the electrodes, is being utilized in a greater degree in the manufacturing of automotive vehicles. Spot-welding requires a frame design that is conducive to being manufactured using the spot-welding process. For example, if two tubular members are being spot-welded, access to the adjoining walls of the two tubular members by the spot-welder electrodes must be provided.
The joining of hydroformed frame members presents a problem for frame construction in automobiles. If the frame members are positioned in a parallel orientation in an overlapping arrangement, the contiguous sides of the two frame members can be spot-welded together with the electrodes being inserted through openings formed during the hydroforming process in the respective opposing sides of the frame members. This overlapping of hydroformed frame members requires spatial consideration for accommodating large tubular frame members in a side-by-side relationship.
Tubular front rail sections have proven to provide cost and weight advantages over traditional stamped and welded front end structures. The challenge associated with the use of hydroformed tubular members is the joining of those tubular members to the rest of the body structure while maintaining current manufacturing processes and minimizing design changes and investment costs to form the automotive frame. It is also desirable to provide a frame design that will enhance the stiffness of the welded frame structure by providing a stiffer joint between joined frame members.
Accordingly, it would be desirable to provide an automotive frame that incorporates a hydroformed front rail member that can be joined to the existing body inner side (rocker) beam without requiring substantive re-design of the frame structure.